In order to use an LED chip in a circuit or other like arrangement, it is known to enclose an LED chip in a package to provide environmental and/or mechanical protection, color selection, light focusing and the like. An LED package also includes electrical leads, contacts or traces for electrically connecting the LED package to an external circuit.
Some LED packages (e.g. XLamp™ LEDs provided by Cree, Inc.) incorporate one LED chip and higher light output is achieved at the assembly level by mounting several of these LED packages onto a single circuit board. Other LED packages comprise arrays of many LED packages. Alternatively, higher flux components have been provided by utilizing arrays of cavities, with a single LED chip mounted in each of the cavities. (e.g., TitanTurbo™. LED Light Engines provided by Lamina, Inc.)
It is also generally observed that LED's perform best when operating temperatures are minimized. Thus, it is generally desirable to remove heat from the LED, typically by heat transfer via the substrate or submount. One of the best ceramic substrates for heat transfer is aluminum nitride (AlN). However, at least one problem with AlN as a heat transfer material in a LED package is that it is not very reflective, which absorbs visible light and reduces the total luminous flux of the package. Conventional technology is to cover as much of the heat transfer material and/or dead space areas with reflective metal, or with white soldermask to maximize reflectivity while at the same time providing heat transfer. Unfortunately, metal cannot be applied everywhere in high density LED packages due to its electrical conductive properties. There is also a significant amount of area (e.g., known as “canyon walls”) between light emitting elements that also absorb or poorly reflect the luminous light. These conventional solutions are, for the most part, inadequate for maximizing the total luminous flux of a solid state lighting package.